<template>
	<view class="v-wrap">
		<view class="v-search-box">
			<view class="v-search-inner">
				<v-icon name="search" color="#909399" :size="28"></v-icon>
				<text class="v-search-text">搜索</text>
			</view>
		</view>
		<view class="v-menu-wrap">
			<scroll-view
				scroll-y
				scroll-with-animation
				class="v-tab-view menu-scroll-view"
				:scroll-top="scrollTop"
				:scroll-into-view="itemId"
			>
				<view
					v-for="(item, index) in tabbar"
					:key="index"
					class="v-tab-item"
					:class="[current == index ? 'v-tab-item-active' : '']"
					@tap.stop="swichMenu(index)"
				>
					<text class="v-line-1">{{ item.name }}</text>
				</view>
			</scroll-view>
			<scroll-view
				:scroll-top="scrollRightTop"
				scroll-y
				scroll-with-animation
				class="right-box"
				@scroll="rightScroll"
			>
				<view class="page-view">
					<view
						class="class-item"
						:id="'item' + index"
						v-for="(item, index) in tabbar"
						:key="index"
					>
						<view class="item-title">
							<text>{{ item.name }}</text>
						</view>
						<view class="item-container">
							<view
								class="thumb-box"
								v-for="(item1, index1) in item.foods"
								:key="index1"
							>
								<image
									class="item-menu-image"
									:src="item1.icon"
									mode=""
								></image>
								<view class="item-menu-name">{{
									item1.name
								}}</view>
							</view>
						</view>
					</view>
				</view>
			</scroll-view>
		</view>
	</view>
</template>
<script>
import classifyData from "@/common/classify.data.js";
export default {
	data() {
		return {
			scrollTop: 0, //tab标题的滚动条位置
			oldScrollTop: 0,
			current: 0, // 预设当前项的值
			menuHeight: 0, // 左边菜单的高度
			menuItemHeight: 0, // 左边菜单item的高度
			itemId: "", // 栏目右边scroll-view用于滚动的id
			tabbar: classifyData,
			menuItemPos: [],
			arr: [],
			scrollRightTop: 0, // 右边栏目scroll-view的滚动条高度
			timer: null, // 定时器
		};
	},
	onLoad() {},
	onReady() {
		this.getMenuItemTop();
	},
	methods: {
		// 点击左边的栏目切换
		async swichMenu(index) {
			if (this.arr.length == 0) {
				await this.getMenuItemTop();
			}
			if (index == this.current) return;
			this.scrollRightTop = this.oldScrollTop;
			this.$nextTick(function () {
				this.scrollRightTop = this.arr[index];
				this.current = index;
				this.leftMenuStatus(index);
			});
		},
		// 获取一个目标元素的高度
		getElRect(elClass, dataVal) {
			new Promise((resolve, reject) => {
				const query = uni.createSelectorQuery().in(this);
				query
					.select("." + elClass)
					.fields(
						{
							size: true,
						},
						(res) => {
							// 如果节点尚未生成，res值为null，循环调用执行
							if (!res) {
								setTimeout(() => {
									this.getElRect(elClass);
								}, 10);
								return;
							}
							this[dataVal] = res.height;
							resolve();
						}
					)
					.exec();
			});
		},
		// 观测元素相交状态
		async observer() {
			this.tabbar.map((val, index) => {
				let observer = uni.createIntersectionObserver(this);
				// 检测右边scroll-view的id为itemxx的元素与right-box的相交状态
				// 如果跟.right-box底部相交，就动态设置左边栏目的活动状态
				observer
					.relativeTo(".right-box", {
						top: 0,
					})
					.observe("#item" + index, (res) => {
						if (res.intersectionRatio > 0) {
							let id = res.id.substring(4);
							this.leftMenuStatus(id);
						}
					});
			});
		},
		// 设置左边菜单的滚动状态
		async leftMenuStatus(index) {
			this.current = index;
			// 如果为0，意味着尚未初始化
			if (this.menuHeight == 0 || this.menuItemHeight == 0) {
				await this.getElRect("menu-scroll-view", "menuHeight");
				await this.getElRect("v-tab-item", "menuItemHeight");
			}
			// 将菜单活动item垂直居中
			this.scrollTop =
				index * this.menuItemHeight +
				this.menuItemHeight / 2 -
				this.menuHeight / 2;
		},
		// 获取右边菜单每个item到顶部的距离
		getMenuItemTop() {
			new Promise((resolve) => {
				let selectorQuery = uni.createSelectorQuery();
				selectorQuery
					.selectAll(".class-item")
					.boundingClientRect((rects) => {
						// 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
						if (!rects.length) {
							setTimeout(() => {
								this.getMenuItemTop();
							}, 10);
							return;
						}
						rects.forEach((rect) => {
							// 这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
							this.arr.push(rect.top - rects[0].top);
							resolve();
						});
					})
					.exec();
			});
		},
		// 右边菜单滚动
		async rightScroll(e) {
			this.oldScrollTop = e.detail.scrollTop;
			if (this.arr.length == 0) {
				await this.getMenuItemTop();
			}
			if (this.timer) return;
			if (!this.menuHeight) {
				await this.getElRect("menu-scroll-view", "menuHeight");
			}
			setTimeout(() => {
				// 节流
				this.timer = null;
				// scrollHeight为右边菜单垂直中点位置
				let scrollHeight = e.detail.scrollTop + this.menuHeight / 2;
				for (let i = 0; i < this.arr.length; i++) {
					let height1 = this.arr[i];
					let height2 = this.arr[i + 1];
					// 如果不存在height2，意味着数据循环已经到了最后一个，设置左边菜单为最后一项即可
					if (
						!height2 ||
						(scrollHeight >= height1 && scrollHeight < height2)
					) {
						this.leftMenuStatus(i);
						return;
					}
				}
			}, 10);
		},
	},
};
</script>

<style lang="scss" scoped>
.v-wrap {
	height: calc(100vh);
	/* #ifdef H5 */
	height: calc(100vh - var(--window-top));
	/* #endif */
	display: flex;
	flex-direction: column;
}

.v-search-box {
	padding: 18rpx 30rpx;
}

.v-menu-wrap {
	flex: 1;
	display: flex;
	overflow: hidden;
}

.v-search-inner {
	background-color: rgb(234, 234, 234);
	border-radius: 100rpx;
	display: flex;
	align-items: center;
	padding: 10rpx 16rpx;
}

.v-search-text {
	font-size: 26rpx;
	color: $v-tips-color;
	margin-left: 10rpx;
}

.v-tab-view {
	width: 200rpx;
	height: 100%;
}

.v-tab-item {
	height: 110rpx;
	background: #f6f6f6;
	box-sizing: border-box;
	display: flex;
	align-items: center;
	justify-content: center;
	font-size: 26rpx;
	color: #444;
	font-weight: 400;
	line-height: 1;
}

.v-tab-item-active {
	position: relative;
	color: #000;
	font-size: 30rpx;
	font-weight: 600;
	background: #fff;
}

.v-tab-item-active::before {
	content: "";
	position: absolute;
	border-left: 4px solid $v-primary;
	height: 32rpx;
	left: 0;
	top: 39rpx;
}

.v-tab-view {
	height: 100%;
}

.right-box {
	background-color: rgb(250, 250, 250);
}

.page-view {
	padding: 16rpx;
}

.class-item {
	margin-bottom: 30rpx;
	background-color: #fff;
	padding: 16rpx;
	border-radius: 8rpx;
}

.class-item:last-child {
	min-height: 100vh;
}

.item-title {
	font-size: 26rpx;
	color: $v-main-color;
	font-weight: bold;
}

.item-menu-name {
	font-weight: normal;
	font-size: 24rpx;
	color: $v-main-color;
}

.item-container {
	display: flex;
	flex-wrap: wrap;
}

.thumb-box {
	width: 33.333333%;
	display: flex;
	align-items: center;
	justify-content: center;
	flex-direction: column;
	margin-top: 20rpx;
}

.item-menu-image {
	width: 120rpx;
	height: 120rpx;
}
</style>
